1. Field of the Invention
The present invention relates to a liquid ejection apparatus and a liquid tank, and more particularly to a liquid ejection apparatus and liquid tank which remove foreign matter from a collected liquid so that the liquid can be reused.
2. Description of the Related Art
When discarded ink is collected for reuse in an ink ejection apparatus comprising ink ejection nozzles, foreign matter such as viscous ink lumps and paper particles are typically contained in the discarded ink. Therefore, if the ink containing such foreign matter is reused as is, the ink ejection nozzles become blocked, leading to defective ink ejection. Hence, apparatuses comprising a filter for removing foreign matter from discarded ink have been proposed.
Japanese Patent Application Publication No. 2-281960 discloses an apparatus formed with an ink collection chamber in the upper portion of an ink cartridge and an ink supply chamber in the lower portion of the ink cartridge. A filter (filtration member) is provided in a connecting portion which leads from the bottom surface of the ink collection chamber into the ink supply chamber.
Japanese Patent Application Publication No. 2001-315357 discloses an apparatus in which a filter is provided in a flow passage through which discarded ink ejected from an ink ejection head is collected in an ink cartridge, and a pump for removing the foreign matter that accumulates in the filter is provided upstream or downstream of the filter. The foreign matter removed from the filter by driving the pump is discharged together with the discarded ink.
Japanese Patent Application Publication No. 2002-200771 discloses an apparatus comprising a tank (sub-tank) which supplies ink to an ink ejection head, and a tank (discarded ink tank) which collects ink ejected from the ink ejection head. A filter is provided in a connecting portion which connects the two tanks, and a pump is provided to discharge the discarded ink intermixed with foreign matter from the discarded ink tank.
Japanese Patent Application Publication No. 2001-315358 discloses an apparatus in which a filter is disposed in a flow passage through which ink ejected from an ink ejection head is collected in an ink cartridge, and a device for reducing the viscosity of the ink along the flow passage is provided upstream of the filter.
Japanese Patent Application Publication No. 2002-240318 discloses an apparatus in which a filter is disposed in a flow passage through which ink ejected from an ink ejection head is collected in an ink storage tank, and a user is encouraged to replace the filter when the flow velocity of the ink through the flow passage decreases below a predetermined threshold.
As the number of nozzles which eject the ink increases, the amount of discarded ink generated during a restoration operation such as a dry discharge or suction also increases. The foreign matter intermixed in the discarded ink is trapped by the filter, but the filter becomes blocked by the trapped foreign matter, and therefore the filter must be replaced with increasing frequency as the amount of discarded ink increases.
In the apparatus described in Japanese Patent Application Publication No. 2-281960, the foreign matter that flows into the ink collection chamber together with the collected ink settles on the bottom surface of the ink collection chamber, and as a result, the filter disposed in the connecting portion leading from the bottom surface of the ink collection chamber into the ink supply chamber becomes blocked easily by the foreign matter. This filter is provided inside the ink cartridge, and hence it is impossible to replace the filter alone when the foreign matter blocks the filter. As a result, the whole ink cartridge must be replaced, even when usable ink remains in the ink cartridge.
In the apparatuses described in Japanese Patent Application Publication Nos. 2001-315357 and 2002-200771, ink is discharged together with the removed foreign matter, and therefore the ink consumption increases.
In the apparatus described in Japanese Patent Application Publication No. 2001-315358, the viscosity of the collected ink is reduced along the flow passage, and re-melting of the impurities that are separated by evaporation requires a large amount of time. Therefore, this apparatus is inadequate.
In the apparatus described in Japanese Patent Application Publication No. 2002-240318, the user is encouraged to replace the filter with great frequency when the amount of discarded ink increases.